This invention relates to a positioning apparatus and more particularly to the combination LCD screen and keyboard cover (hereinafter referred to as combination keyboard cover) of a lap top computer with a tilt-angle adjusting apparatus for adjusting the degree of the tilt.
Normally, the prior art lap top computer as shown in FIG. 6, comprises the combination keyboard cover 3 which is hinged to the main body 1. An LCD screen 4 is fixed to the inner face of the combination keyboard cover 3. The combination keyboard cover 3 can be used as either an LCD screen when opened or a keyboard cover when closed.
In using the combination keyboard cover of a lap top computer, it becomes more essential that an operator is able to alter the viewing angle of the screen surface to obtain the desired angle of tilt on the screen and that the tilt screen be held in the desired position with maximum stability.
In the tilt-angle adjusting apparatus, the prior art lap top computer can have either a tight fit mechanism or a detent mechanism which is built into the computer. In the case of tight fit mechanism, it becomes difficult to manufacture hinge shafts and mating holes which meet the prescribed tolerance limits. Another disadvantage is that the fit between the hinge shafts and mating holes loosens over a long period of use, thus causing the collapse of the combination keyboard cover under its own weight.
On the other hand, while the detent mechanism eliminates the need for a special hinge shaft or a mating hole structure, it has the disadvantage that the elasticity between ratchet and claw descreases over a long period of use, thus preventing the tilt screen from being adjusted in the desired tilt position and held there with stability. Also, the two mechanisms are almost unmendable once they break down.
Another disadvantage is that the prior art lap top computer needs to have a high overall height for facilitating the pivotal movement of the combination cover 4 because the hinge point is constructed to be immovable.
It is the main object of the present invention to provide a pivotable combination LCD screen and keyboard cover which is readily adjustable in position and stably held in place over a long period of use.
It is another object of the present invention to provide a pivotable combination LCD screen and keyboard cover which is simple in construction, low in manufacturing cost and compact in size.